Printing system and method using alternating velocity and torque control modes for operating one or more select sheet transport devices to avoid contention

Abstract

A printing system and method using alternating control modes for one or more, but not all, sheet transport devices in order to avoid contention. In a printer having first, second and third sheet transport devices in series (e.g., registration, image transfer and image fixing devices), the second device can always operate in a velocity control mode. However, the first and/or third devices can alternate between velocity and torque control modes. For example, the first device can operate in a torque control mode, when a sheet is concurrently engaged by both the first and second devices, and in a velocity control mode at other times. Additionally or alternatively, the third device can operate in a torque control mode, when a sheet is concurrently engaged by both the second and third devices, and in a velocity control mode at other times. Transition control modes can be implemented to generate smooth transitions between modes.

1. A printing method comprising:
 independently controlling multiple sheet transport devices transporting a print media sheet along a sheet transport path, said sheet transport devices comprising a first sheet transport device, a second sheet transport device and a third sheet transport device in series and said independently controlling comprising, during a printing operation, 
 controlling said second sheet transport device solely using a velocity control mode such that said velocity control mode is used as said second sheet transport device receives said print media sheet from said first sheet transport device, when both said second sheet transport device and said first sheet transport device concurrently engage said print media sheet, and further such that said velocity control mode is used as said second sheet transport device transports said print media sheet to said third sheet transport device, when both said second sheet transport device and said third sheet transport device concurrently engage said print media sheet; and 
 controlling any one of said first sheet transport device and said third sheet transport device alternatingly using a velocity control mode and a torque control mode. 
 
     
     
       2. The method of  claim 1 , said using of said velocity control mode comprising selectively adjusting drive roller angular velocity in order to achieve any one of a predetermined constant sheet velocity and a predetermined sheet velocity profile. 
     
     
       3. The method  claim 1 , said using of said torque control mode comprising any one of the following:
 applying a constant set point level of torque to said one of said first sheet transport device and said third sheet transport device based on a previously measured and recorded level of torque applied to said one of said first sheet transport device and said third sheet transport device during said velocity control mode; and 
 supplying a constant set point level of power to said one of said first sheet transport device and said third sheet transport device based on a previously measured and recorded level of power supplied to said one of said first sheet transport device and said third sheet transport device during said velocity control mode. 
 
     
     
       4. The method of  claim 1 , said using of said torque control mode comprising any one of the following:
 applying a level of torque to said one of said first sheet transport device and said third sheet transport device based on a measured level of torque applied to said second sheet transport device; and 
 supplying a level of power to said one of said first sheet transport device and said third sheet transport device based on a measured level of power supplied to said second sheet transport device. 
 
     
     
       5. The method of  claim 1 , said using of said torque control mode comprising applying any one of a varying level of torque and a varying level of power to said one of said first sheet transport device and said third sheet transport device so that a desired level of sheet tension is maintained at said second sheet transport device. 
     
     
       6. The method of  claim 1 , said controlling of said one of said first sheet transport device and said third sheet transport device comprising using a transition control mode when transitioning from said velocity control mode to said torque control mode and further when transitioning from said torque control mode to said velocity control mode. 
     
     
       7. The method of  claim 1 , said first sheet transport device comprising a registration device, said second sheet transport device comprising an image transfer device and said third sheet transport device comprising an image fixing device. 
     
     
       8. A method comprising:
 independently controlling multiple sheet transport devices transporting a print media sheet along a sheet transport path, said sheet transport devices comprising a first sheet transport device, a second sheet transport device and a third sheet transport device in series and said independently controlling comprising:
 controlling said first sheet transport device as said first sheet transport device receives a print media sheet and transports said print media sheet to said second sheet transport device, said controlling of said first sheet transport device comprising alternatingly using a velocity control mode and a torque control mode; 
 controlling said second sheet transport device as said second sheet transport device receives said print media sheet from said first sheet transport device and transports said print media sheet to said third sheet transport device, said controlling of said second sheet transport device comprising solely using said velocity control mode; and 
 controlling said third sheet transport device as said third sheet transport device receives said print media sheet from said second sheet transport device and further transports said print media sheet, said controlling of said third sheet transport device comprising alternatingly using said torque control mode and said velocity control mode. 
 
 
     
     
       9. The method of  claim 8 ,
 said controlling of said first sheet transport device further comprising: using said velocity control mode, when said print media sheet is not concurrently engaged by said second sheet transport device; and using said torque control mode, when said print media sheet is concurrently engaged by both said first sheet transport device and said second sheet transport device, 
 said controlling of said second sheet transport device further comprising: using said velocity control mode, when both said second sheet transport device and said first sheet transport device concurrently engage said print media sheet and when both said second sheet transport device and said third sheet transport device concurrently engage said print media sheet, and 
 said controlling of said third sheet transport device further comprising: using said torque control mode, when said print media sheet is concurrently engaged by both said second sheet transport device and said third sheet transport device, and using said velocity control mode, when said print media sheet is not concurrently engaged by said second sheet transport device. 
 
     
     
       10. The method of  claim 8 , said using of said velocity control mode comprising selectively adjusting drive roller angular velocity in order to achieve any one of a predetermined constant sheet velocity and a predetermined sheet velocity profile. 
     
     
       11. The method  claim 8 , said using of said torque control mode comprising any one of the following:
 applying a constant set point level of torque to a corresponding one said first sheet transport device and said third sheet transport device based on a previously measured and recorded level of torque applied to said corresponding one said first sheet transport device and said third sheet transport device during said velocity control mode; 
 supplying a constant set point level of power to a corresponding one said first sheet transport device and said third sheet transport device based on a previously measured and recorded level of power supplied to said corresponding one of said first sheet transport device and said third sheet transport device during said velocity control mode; 
 applying a level of torque to a corresponding one of said first sheet transport device and said third sheet transport device based on a measured level of torque applied to said second sheet transport device; 
 supplying a level of power to a corresponding one of said first sheet transport device and said third sheet transport device based on a measured level of power supplied to said second sheet transport device. 
 
     
     
       12. The method of  claim 8 , said using of said torque control mode comprising any one of applying a varying level of torque to a corresponding one of said first sheet transport device and said third sheet transport device and supplying a varying level of power to said corresponding one of said first sheet transport device and said third sheet transport device so that a desired level of sheet tension is maintained at said second sheet transport device. 
     
     
       13. The method of  claim 8 , said controlling of said first sheet transport device and said controlling of said third sheet transport device each comprising using a transition control mode when transitioning from said velocity control mode to said torque control mode and further when transitioning from said torque control mode to said velocity control mode. 
     
     
       14. The method of  claim 8 , said first sheet transport device comprising a registration device, said second sheet transport device comprising an image transfer device and said third sheet transport device comprising an image fixing device. 
     
     
       15. A printer comprising:
 multiple sheet transport devices transporting a print media sheet along a sheet transport path, said sheet transport devices comprising a first sheet transport device, a second sheet transport device and a third sheet transport device in series; and 
 at least one controller controlling said multiple sheet transport devices as follows:
 controlling said second sheet transport device solely using a velocity control mode such that said velocity control mode is used as said second sheet transport device receives said print media sheet from said first sheet transport device, when both said second sheet transport device and said first sheet transport device concurrently engage said print media sheet, and further such that said velocity control mode is used as said second sheet transport device transports said print media sheet to said third sheet transport device, when both said second sheet transport device and said third sheet transport device concurrently engage said print media sheet; and 
 controlling any one of said first sheet transport device and said third sheet transport device alternatingly using a velocity control mode and a torque control mode. 
 
 
     
     
       16. The printer of  claim 15 , said at least one controller causing, in said velocity control mode, drive roller angular velocity to be selectively adjusted in order to achieve any one of a predetermined constant sheet velocity and a predetermined sheet velocity profile. 
     
     
       17. The printer of  claim 15 , said at least one controller causing, in said torque control mode, any one of the following:
 a constant set point level of torque to be applied to said one of said first sheet transport device and said third sheet transport device based on a previously measured and recorded level of torque applied to said one of said first sheet transport device and said third sheet transport device during said velocity control mode; and 
 a constant set point level of power to be supplied to said one of said first sheet transport device and said third sheet transport device based on a previously measured and recorded level of power supplied to said one of said first sheet transport device and said third sheet transport device during said velocity control mode. 
 
     
     
       18. The printer of  claim 15 , said at least one controller causing, in said torque control mode, any one of the following:
 a level of torque to be applied to said one of said first sheet transport device and said third sheet transport device based on a measured level of torque applied to said second sheet transport device; and 
 a level of power to be supplied to said one of said first sheet transport device and said third sheet transport device based on a measured level of power supplied to said second sheet transport device. 
 
     
     
       19. The printer of  claim 15 , said at least one controller causing, in said torque control mode, any one of a varying level of torque to be applied to said one of said first sheet transport device and said third sheet transport device and a varying level of power to be supplied to said one of said first sheet transport device and said third sheet transport device so that a desired level of sheet tension is maintained at said second sheet transport device. 
     
     
       20. The printer of  claim 15 , said at least one controller further controlling said one of said first sheet transport device and said third sheet transport device comprising using a transition control mode when transitioning from said velocity control mode to said torque control mode and further when transitioning from said torque control mode to said velocity control mode. 
     
     
       21. The printer of  claim 15 , said first sheet transport device comprising a registration device, said second sheet transport device comprising an image transfer device and said third sheet transport device comprising an image fixing device. 
     
     
       22. A printer comprising:
 multiple sheet transport devices transporting a print media sheet along a sheet transport path, said sheet transport devices comprising a first sheet transport device, a second sheet transport device and a third sheet transport device in series; and 
 at least one controller performing the following:
 controlling said first sheet transport device as said first sheet transport device receives a print media sheet and transports said print media sheet to said second sheet transport device, said controlling of said first sheet transport device comprising alternatingly using a velocity control mode and a torque control mode; 
 controlling said second sheet transport device as said second sheet transport device receives said print media sheet from said first sheet transport device and transports said print media sheet to said third sheet transport device, said controlling of said second sheet transport device comprising solely using said velocity control mode; and 
 controlling said third sheet transport device as said third sheet transport device receives said print media sheet from said second sheet transport device and further transports said print media sheet, said controlling of said third sheet transport device comprising alternatingly using said torque control mode and said velocity control mode. 
 
 
     
     
       23. The printer of  claim 22 ,
 said at least one controller controlling said first sheet transport device using said velocity control mode, when said print media sheet is not engaged by said second sheet transport device, and using said torque control mode, when said print media sheet is concurrently engaged by both said first sheet transport device and said second sheet transport device, 
 said at least one controller controlling said second sheet transport device using said velocity control mode, when both said second sheet transport device and said first sheet transport device concurrently engage said print media sheet and when both said second sheet transport device and said third sheet transport device concurrently engage said print media sheet, and 
 said at least one controller controlling said third sheet transport device using said torque control mode, when said print media sheet is concurrently engaged by both said second sheet transport device and said third sheet transport device, and using said velocity control mode, when said print media sheet is not engaged by said second sheet transport device.